Like the noise makers that are along the edge of the highway.
 

Over the last month my 99 Expy Eddie Bauer, with airbag rear has been making this intermittant noise from somewhere underneath. It happens while I'm accelerating and seems to be during a upshift but not always. The sound it makes is like when you go to far to the side of the highway and hit the wakeup divits or when you approach a toll both and it has the slow down bumps. It only last for about 1.5 seconds and then quits. You can feel it through the seat when it happens and is pretty pronounced. Any of you guys have any idea?

Thanks

Hmmmm...
 

My best guess might be the dreaded tranny shudder...but it shouldn't really make a noise...more a vibration that is felt in the seat of the pants.

The only reason I say tranny shudder is that it tends to happen during acceleration and a downshift. It's brief and annoying.

The sound that you say it makes is a bit disconcerting to me...hopefully someone else will be more enilightening.

:beers:

Been there, done that on a 2000 Expy I had. Go have your tranny flushed and that should fix the problem. Don't know why, but when the fluid gets old it effects the torque converter and causes a shudder. I use a local Valvoline Lube center and when I mentioned it to the tech he knew all about it. Ford may have a TSB on it, I'm not sure. All I know is after I had the tranny flushed, (about $150.00), the problem went away. Just make sure it is flushed and not just drain the fluid and change the filter.

Good Luck!

I agree about the tranny shudder. It's a well known problem on Mark VIII's, and when my wife told me her's was doing it I just changed the fluid and put in fresh. Had been planning to do it anyway, and it made the problem go away.

Thanks for the reply's. It only happens when the trans shifts during acceleration. It is most pronounced during the shift into 3rd. I bought it used and am not sure if the trans has been serviced in the past. It has 82K mi and that makes me scared to flush without knowing the trans service history. Should I still flush it?

Thanks

Definately flush it as soon as possible.

Will do